How can we insert an item into an array efficiently?

Sometimes we have to insert items to the first indices of the array

The easiest solution can be:

  var array = [1,2,3,4,5,6,7,8,9]
  array.insert(0, at: 0)
  print(array)

this solution is going to work, but is it efficient?

Looking into the Apple Documentation of the insert function you can see the complexity of the insert function is O(n) which means all elements of the array will be shifted to insert the item to index 0

So the solution is not efficient, so how can we improve it?

One possible solution is using reverse function whose complexity is O(1) so it's very efficient

1. First, reverse the array
2. Then append the item to the array
3. Then reverse the array again

   var array = [1,2,3,4,5,6,7,8,9]
   array.reverse()
   array.append(0)
   array.reverse()
   print(array)
   

   That is it!